Structural shapes such as angle-profile bars, frequently referred to as angle profiles, can have flanges of equal width or, in terms of the cross section or profile, of equal length, lying at right angles to one another at a vertex.
In general, such structural shapes have radiused junctions at the inside of the vertex and rounded free ends along the inner edges of the flanges while the backs of the flanges, forming the exterior of the profile, meet at a relatively sharp right angle.
Depending upon the loading to which the structural shape is to be subjected, the flange widths and thicknesses can be varied.
The common method of fabricating such structural shapes is by multi-pass rolling in which a steel or iron bar is passed between pairs of rolls with shapes corresponding to the shapes to be imparted to the steel bar at each pass whereby the cross section of the bar is reduced, the bar is lengthened and ultimately the desired angle profile is imparted to the bar.
As will be described in greater detail hereinafter with reference to the initial FIGURES of the drawing, the conventional rollimg methods used heretofore, since the turn of the century, have been relatively complex in spite of the ultimately simple shape of the angle profile. Complicated rolling processes require large numbers of roll stands and for various sizes of the angle profiles, corresponding adjustments in roll spacing, etc. In general, therefore, the rolling cost is significant, the operation is time consuming, and the process is labor intensive.
In earlier systems, the starting billet or bar is of generally rectangular profile and is rolled with cross section reduction in seven or nine steps to the desired angle profile. During most of these steps, the thickness of the "wings" formed to either side of a central triangular or pointed protuberance, is reduced while the protuberance is repeatedly reshaped until it more closely approximates a right angle at its outer flanks so that it can form the vertex of the angle profile.
This was the state of the art insofar as commercial applications of rolling processes to the formation of angle profiles was concerned until my development of a simplified rolling process as described in the aforementioned copending application, which process has not heretofore become part of the prior art. In this application and improved process, a rectangular bar is rolled in a first step to a flat blank having, in the case of angle profiles of equal flange width, a rounded central hump which is of semicircular cross section. In a second step this blank is rolled to reduce the thickness of the wings and impart the right angle configuration to the hump. In a third step the lower outer edges of the wings are rounded and, finally, in a fourth step the wings are bent into the angle configuration in which they assume a right angle with one another.
The advantage of this latter approach is that it markedly reduces the number of passes which have been considered necessary for the rolling of angle profiles, indeed a surprising phenomenon when it is considered that earlier systems have almost unanimously recognized that commercial application required at least seven to nine steps of the type described.